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[6.18] Track PF uksmd patches #42

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ec913df
mm: expose per-process KSM control via syscalls
kakra Dec 14, 2025
e8020af
mm/process_ksm: use pidfd_get_task() instead of pidfd_get_pid()+get_p…
pfactum Sep 24, 2024
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3 changes: 3 additions & 0 deletions arch/alpha/kernel/syscalls/syscall.tbl
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Expand Up @@ -509,3 +509,6 @@
577 common open_tree_attr sys_open_tree_attr
578 common file_getattr sys_file_getattr
579 common file_setattr sys_file_setattr
580 common process_ksm_enable sys_process_ksm_enable
581 common process_ksm_disable sys_process_ksm_disable
582 common process_ksm_status sys_process_ksm_status
3 changes: 3 additions & 0 deletions arch/arm/tools/syscall.tbl
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Expand Up @@ -484,3 +484,6 @@
467 common open_tree_attr sys_open_tree_attr
468 common file_getattr sys_file_getattr
469 common file_setattr sys_file_setattr
470 common process_ksm_enable sys_process_ksm_enable
471 common process_ksm_disable sys_process_ksm_disable
472 common process_ksm_status sys_process_ksm_status
3 changes: 3 additions & 0 deletions arch/m68k/kernel/syscalls/syscall.tbl
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Expand Up @@ -469,3 +469,6 @@
467 common open_tree_attr sys_open_tree_attr
468 common file_getattr sys_file_getattr
469 common file_setattr sys_file_setattr
470 common process_ksm_enable sys_process_ksm_enable
471 common process_ksm_disable sys_process_ksm_disable
472 common process_ksm_status sys_process_ksm_status
3 changes: 3 additions & 0 deletions arch/microblaze/kernel/syscalls/syscall.tbl
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Expand Up @@ -475,3 +475,6 @@
467 common open_tree_attr sys_open_tree_attr
468 common file_getattr sys_file_getattr
469 common file_setattr sys_file_setattr
470 common process_ksm_enable sys_process_ksm_enable
471 common process_ksm_disable sys_process_ksm_disable
472 common process_ksm_status sys_process_ksm_status
3 changes: 3 additions & 0 deletions arch/mips/kernel/syscalls/syscall_n32.tbl
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Expand Up @@ -408,3 +408,6 @@
467 n32 open_tree_attr sys_open_tree_attr
468 n32 file_getattr sys_file_getattr
469 n32 file_setattr sys_file_setattr
470 n32 process_ksm_enable sys_process_ksm_enable
471 n32 process_ksm_disable sys_process_ksm_disable
472 n32 process_ksm_status sys_process_ksm_status
3 changes: 3 additions & 0 deletions arch/mips/kernel/syscalls/syscall_n64.tbl
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Expand Up @@ -384,3 +384,6 @@
467 n64 open_tree_attr sys_open_tree_attr
468 n64 file_getattr sys_file_getattr
469 n64 file_setattr sys_file_setattr
470 n64 process_ksm_enable sys_process_ksm_enable
471 n64 process_ksm_disable sys_process_ksm_disable
472 n64 process_ksm_status sys_process_ksm_status
3 changes: 3 additions & 0 deletions arch/mips/kernel/syscalls/syscall_o32.tbl
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Expand Up @@ -457,3 +457,6 @@
467 o32 open_tree_attr sys_open_tree_attr
468 o32 file_getattr sys_file_getattr
469 o32 file_setattr sys_file_setattr
470 o32 process_ksm_enable sys_process_ksm_enable
471 o32 process_ksm_disable sys_process_ksm_disable
472 o32 process_ksm_status sys_process_ksm_status
3 changes: 3 additions & 0 deletions arch/parisc/kernel/syscalls/syscall.tbl
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Expand Up @@ -468,3 +468,6 @@
467 common open_tree_attr sys_open_tree_attr
468 common file_getattr sys_file_getattr
469 common file_setattr sys_file_setattr
470 common process_ksm_enable sys_process_ksm_enable
471 common process_ksm_disable sys_process_ksm_disable
472 common process_ksm_status sys_process_ksm_status
3 changes: 3 additions & 0 deletions arch/powerpc/kernel/syscalls/syscall.tbl
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Expand Up @@ -560,3 +560,6 @@
467 common open_tree_attr sys_open_tree_attr
468 common file_getattr sys_file_getattr
469 common file_setattr sys_file_setattr
470 common process_ksm_enable sys_process_ksm_enable
471 common process_ksm_disable sys_process_ksm_disable
472 common process_ksm_status sys_process_ksm_status
3 changes: 3 additions & 0 deletions arch/s390/kernel/syscalls/syscall.tbl
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Expand Up @@ -472,3 +472,6 @@
467 common open_tree_attr sys_open_tree_attr sys_open_tree_attr
468 common file_getattr sys_file_getattr sys_file_getattr
469 common file_setattr sys_file_setattr sys_file_setattr
470 common process_ksm_enable sys_process_ksm_enable sys_process_ksm_enable
471 common process_ksm_disable sys_process_ksm_disable sys_process_ksm_disable
472 common process_ksm_status sys_process_ksm_status sys_process_ksm_status
3 changes: 3 additions & 0 deletions arch/sh/kernel/syscalls/syscall.tbl
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Expand Up @@ -473,3 +473,6 @@
467 common open_tree_attr sys_open_tree_attr
468 common file_getattr sys_file_getattr
469 common file_setattr sys_file_setattr
470 common process_ksm_enable sys_process_ksm_enable
471 common process_ksm_disable sys_process_ksm_disable
472 common process_ksm_status sys_process_ksm_status
3 changes: 3 additions & 0 deletions arch/sparc/kernel/syscalls/syscall.tbl
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Expand Up @@ -515,3 +515,6 @@
467 common open_tree_attr sys_open_tree_attr
468 common file_getattr sys_file_getattr
469 common file_setattr sys_file_setattr
470 common process_ksm_enable sys_process_ksm_enable
471 common process_ksm_disable sys_process_ksm_disable
472 common process_ksm_status sys_process_ksm_status
3 changes: 3 additions & 0 deletions arch/x86/entry/syscalls/syscall_32.tbl
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Expand Up @@ -475,3 +475,6 @@
467 i386 open_tree_attr sys_open_tree_attr
468 i386 file_getattr sys_file_getattr
469 i386 file_setattr sys_file_setattr
470 i386 process_ksm_enable sys_process_ksm_enable
471 i386 process_ksm_disable sys_process_ksm_disable
472 i386 process_ksm_status sys_process_ksm_status
3 changes: 3 additions & 0 deletions arch/x86/entry/syscalls/syscall_64.tbl
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Expand Up @@ -394,6 +394,9 @@
467 common open_tree_attr sys_open_tree_attr
468 common file_getattr sys_file_getattr
469 common file_setattr sys_file_setattr
470 common process_ksm_enable sys_process_ksm_enable
471 common process_ksm_disable sys_process_ksm_disable
472 common process_ksm_status sys_process_ksm_status

#
# Due to a historical design error, certain syscalls are numbered differently
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3 changes: 3 additions & 0 deletions arch/xtensa/kernel/syscalls/syscall.tbl
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Expand Up @@ -440,3 +440,6 @@
467 common open_tree_attr sys_open_tree_attr
468 common file_getattr sys_file_getattr
469 common file_setattr sys_file_setattr
470 common process_ksm_enable sys_process_ksm_enable
471 common process_ksm_disable sys_process_ksm_disable
472 common process_ksm_status sys_process_ksm_status
3 changes: 3 additions & 0 deletions include/linux/syscalls.h
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Expand Up @@ -838,6 +838,9 @@ asmlinkage long sys_madvise(unsigned long start, size_t len, int behavior);
asmlinkage long sys_process_madvise(int pidfd, const struct iovec __user *vec,
size_t vlen, int behavior, unsigned int flags);
asmlinkage long sys_process_mrelease(int pidfd, unsigned int flags);
asmlinkage long sys_process_ksm_enable(int pidfd, unsigned int flags);
asmlinkage long sys_process_ksm_disable(int pidfd, unsigned int flags);
asmlinkage long sys_process_ksm_status(int pidfd, unsigned int flags);
asmlinkage long sys_remap_file_pages(unsigned long start, unsigned long size,
unsigned long prot, unsigned long pgoff,
unsigned long flags);
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9 changes: 8 additions & 1 deletion include/uapi/asm-generic/unistd.h
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Expand Up @@ -858,8 +858,15 @@ __SYSCALL(__NR_file_getattr, sys_file_getattr)
#define __NR_file_setattr 469
__SYSCALL(__NR_file_setattr, sys_file_setattr)

#define __NR_process_ksm_enable 470
__SYSCALL(__NR_process_ksm_enable, sys_process_ksm_enable)
#define __NR_process_ksm_disable 471
__SYSCALL(__NR_process_ksm_disable, sys_process_ksm_disable)
#define __NR_process_ksm_status 472
__SYSCALL(__NR_process_ksm_status, sys_process_ksm_status)

#undef __NR_syscalls
#define __NR_syscalls 470
#define __NR_syscalls 473

/*
* 32 bit systems traditionally used different
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138 changes: 138 additions & 0 deletions kernel/sys.c
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Expand Up @@ -2876,6 +2876,144 @@ SYSCALL_DEFINE5(prctl, int, option, unsigned long, arg2, unsigned long, arg3,
return error;
}

#ifdef CONFIG_KSM
enum pkc_action {
PKSM_ENABLE = 0,
PKSM_DISABLE,
PKSM_STATUS,
};

static long do_process_ksm_control(int pidfd, enum pkc_action action)
{
long ret;
struct task_struct *task;
struct mm_struct *mm;
unsigned int f_flags;

task = pidfd_get_task(pidfd, &f_flags);
if (IS_ERR(task)) {
ret = PTR_ERR(task);
goto out;
}

/* Require PTRACE_MODE_READ to avoid leaking ASLR metadata. */
mm = mm_access(task, PTRACE_MODE_READ_FSCREDS);
if (IS_ERR_OR_NULL(mm)) {
ret = IS_ERR(mm) ? PTR_ERR(mm) : -ESRCH;
goto release_task;
}

/* Require CAP_SYS_NICE for influencing process performance. */
if (!capable(CAP_SYS_NICE)) {
ret = -EPERM;
goto release_mm;
}

if (mmap_write_lock_killable(mm)) {
ret = -EINTR;
goto release_mm;
}

switch (action) {
case PKSM_ENABLE:
ret = ksm_enable_merge_any(mm);
break;
case PKSM_DISABLE:
ret = ksm_disable_merge_any(mm);
break;
case PKSM_STATUS:
ret = mm_flags_test(MMF_VM_MERGE_ANY, mm);
break;
}

mmap_write_unlock(mm);

release_mm:
mmput(mm);
release_task:
put_task_struct(task);
out:
return ret;
}
#endif /* CONFIG_KSM */

SYSCALL_DEFINE2(process_ksm_enable, int, pidfd, unsigned int, flags)
{
#ifdef CONFIG_KSM
if (flags != 0)
return -EINVAL;

return do_process_ksm_control(pidfd, PKSM_ENABLE);
#else /* CONFIG_KSM */
return -ENOSYS;
#endif /* CONFIG_KSM */
}

SYSCALL_DEFINE2(process_ksm_disable, int, pidfd, unsigned int, flags)
{
#ifdef CONFIG_KSM
if (flags != 0)
return -EINVAL;

return do_process_ksm_control(pidfd, PKSM_DISABLE);
#else /* CONFIG_KSM */
return -ENOSYS;
#endif /* CONFIG_KSM */
}

SYSCALL_DEFINE2(process_ksm_status, int, pidfd, unsigned int, flags)
{
#ifdef CONFIG_KSM
if (flags != 0)
return -EINVAL;

return do_process_ksm_control(pidfd, PKSM_STATUS);
#else /* CONFIG_KSM */
return -ENOSYS;
#endif /* CONFIG_KSM */
}

#ifdef CONFIG_KSM
static ssize_t process_ksm_enable_show(struct kobject *kobj,
struct kobj_attribute *attr, char *buf)
{
return sprintf(buf, "%u\n", __NR_process_ksm_enable);
}
static struct kobj_attribute process_ksm_enable_attr = __ATTR_RO(process_ksm_enable);

static ssize_t process_ksm_disable_show(struct kobject *kobj,
struct kobj_attribute *attr, char *buf)
{
return sprintf(buf, "%u\n", __NR_process_ksm_disable);
}
static struct kobj_attribute process_ksm_disable_attr = __ATTR_RO(process_ksm_disable);

static ssize_t process_ksm_status_show(struct kobject *kobj,
struct kobj_attribute *attr, char *buf)
{
return sprintf(buf, "%u\n", __NR_process_ksm_status);
}
static struct kobj_attribute process_ksm_status_attr = __ATTR_RO(process_ksm_status);

static struct attribute *process_ksm_sysfs_attrs[] = {
&process_ksm_enable_attr.attr,
&process_ksm_disable_attr.attr,
&process_ksm_status_attr.attr,
NULL,
};

static const struct attribute_group process_ksm_sysfs_attr_group = {
.attrs = process_ksm_sysfs_attrs,
.name = "process_ksm",
};

static int __init process_ksm_sysfs_init(void)
{
return sysfs_create_group(kernel_kobj, &process_ksm_sysfs_attr_group);
}
subsys_initcall(process_ksm_sysfs_init);
#endif /* CONFIG_KSM */

SYSCALL_DEFINE3(getcpu, unsigned __user *, cpup, unsigned __user *, nodep,
struct getcpu_cache __user *, unused)
{
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3 changes: 3 additions & 0 deletions kernel/sys_ni.c
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Expand Up @@ -186,6 +186,9 @@ COND_SYSCALL(mincore);
COND_SYSCALL(madvise);
COND_SYSCALL(process_madvise);
COND_SYSCALL(process_mrelease);
COND_SYSCALL(process_ksm_enable);
COND_SYSCALL(process_ksm_disable);
COND_SYSCALL(process_ksm_status);
COND_SYSCALL(remap_file_pages);
COND_SYSCALL(mbind);
COND_SYSCALL(get_mempolicy);
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3 changes: 3 additions & 0 deletions scripts/syscall.tbl
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Expand Up @@ -410,3 +410,6 @@
467 common open_tree_attr sys_open_tree_attr
468 common file_getattr sys_file_getattr
469 common file_setattr sys_file_setattr
470 common process_ksm_enable sys_process_ksm_enable
471 common process_ksm_disable sys_process_ksm_disable
472 common process_ksm_status sys_process_ksm_status
3 changes: 3 additions & 0 deletions tools/perf/arch/powerpc/entry/syscalls/syscall.tbl
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Expand Up @@ -560,3 +560,6 @@
467 common open_tree_attr sys_open_tree_attr
468 common file_getattr sys_file_getattr
469 common file_setattr sys_file_setattr
470 common process_ksm_enable sys_process_ksm_enable
471 common process_ksm_disable sys_process_ksm_disable
472 common process_ksm_status sys_process_ksm_status
3 changes: 3 additions & 0 deletions tools/perf/arch/s390/entry/syscalls/syscall.tbl
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Expand Up @@ -472,3 +472,6 @@
467 common open_tree_attr sys_open_tree_attr sys_open_tree_attr
468 common file_getattr sys_file_getattr sys_file_getattr
469 common file_setattr sys_file_setattr sys_file_setattr
470 common process_ksm_enable sys_process_ksm_enable sys_process_ksm_enable
471 common process_ksm_disable sys_process_ksm_disable sys_process_ksm_disable
472 common process_ksm_status sys_process_ksm_status sys_process_ksm_status